To configure StruxureWare DCE, you need to have a client with a matching version as the server itself. If you have upgraded recently to DCE 7.3.1, you also need to download this new client.
The StruxureWare Data Center Expert 7.3.1 client download was signed in 2016 using an SHA1 hash algorithm.
As per Microsoft Technet:
http://social.technet.microsoft.com/wiki/contents/articles/32288.windows-enforcement-of-authenticode-code-signing-and-timestamping.aspx
Any cert signed after 1.1.2016 should use SHA2.

Resolution:

Unless you want to change the security settings in Internet Explorer to avoid the error entirely, you can download the client file and save it locally and ignore the warning. You can not choose the run option from within IE. At this time, we have also seen no issues with other browsers such as Firefox or Chrome so downloading the client with these browsers should also work.